This invention concerns a composting cage comprising a perforated enclosure divided into a plurality of compartments. It is particularly, but not exclusively suitable for composting biological waste material on an industrial scale, where at least tens of kilograms of such waste are to be loaded per day.
The process of composting is complex. Aerobic bacteria break down the biological material. Thus the material to be composted must be well aerated, not over compacted. This limits the size of any composting container, specifically the width of same in the industrial scale cage with which the invention is primarily concerned. If it is too large, the material in the centre will not have sufficient oxygen and anaerobic processes will ensue which is undesirable. For the same reason, it is important to have a mixture of fine and coarse material. It is also important for purposes of aeration that the material is loaded by sprinkling it in to the top of the cage.
An even distribution of material within the cage is also very important so that there are no higher (deeper) areas of material where it may tend to compact and also so that an evenly degraded layer of material of relatively constant thickness can be regularly removed from the base of the cage.
Loading of the cage has hitherto been carried out by an elongate trough, extending the full width of the cage, and permanently mounted above the cage so as to slide therealong. The trough is loaded with a suitable mixture of material to be composted from a sloping elevator assembly at one end of the cage, and then slides along the top of the cage to dispense the material to one or more selected compartments.
One object of the invention is to provide means for unloading of the trough such that the material therein will be scattered or sprinkled and thereby aerated, but will also be spread as evenly as possible.
Another object of the invention is to tackle a problem associated with removal of composted material from the base of the compartment. This is conventionally accomplished by an auger mounted below the perforated enclosure between respective guide rails and capable of travelling therealong whilst also rotating. Hitherto, the auger has been mounted onto the rails by way of respective motorised trolleys at each end. In order to remove composted material evenly, it is important to try and move the respective ends of the auger at the same rate, so that the axis of the auger remains substantially perpendicular to the direction of travel. Hitherto, this has proved difficult.
According to a first aspect of the invention, the trough has a base formed in part by a plurality of side by side rotors, each having circumferential vanes with radially extending cross walls, whereby the material to be composted can be distributed to the compartments.
In order to prevent material, particularly dry and sandy material, from dropping out between the rotors, the trough preferably has a plurality of flaps mounted below the rotors, these flaps being openable by a lever mechanism upon actuation of the rotors.
Advantageously, a hydraulic lift is provided for raising and lowering the trough between a low level filling station and the top of the cage. At the low level filling station, the trough can be evenly loaded with much greater accuracy, by visual inspection, by means of a conventional mechanical shovel or similar loading equipment.
According to a second aspect of the invention, the auger mounted below the enclosure is now moved intermittently along the respective guide rails by a co-ordinated system of hydraulic rams.
Advantageously, the hydraulic rams, which are arranged at each end of the auger, mounting the auger to the respective guide rails, have a common hydraulic power supply, which links to one of the rams through an axial passage of the auger. In this way the rams will generally move the ends of the auger to the same extent and will not allow them to become significantly out of alignment with each other.
The above mentioned aspects of the invention will all be present in preferred embodiments of composting cage. However, in other embodiments any one of these inventive features may be present on its own, independently of the others.